Fire protection sprinklers may be operated individually, e.g. by a self-contained thermally sensitive element, or as part of a deluge system in which fire retardant fluid flows through a number of open sprinklers, essentially simultaneously. Fire retardant fluids may include natural water or appropriate mixtures of natural water and one or more additives to enhance fire fighting properties of a fire protection system.
Fire protection sprinklers generally include a body with an outlet, an inlet connectable to a source of fire retardant fluid under pressure, and a deflector supported by the body in a position opposing the outlet for distribution of the fire retardant fluid over a predetermined area to be protected from fire Individual fire protection sprinklers may be automatically or non-automatically operating. In the case of automatically operating fire protection sprinklers, the outlet is typically secured in the normally closed or sealed position by a cap. The cap is held in place by a thermally-sensitive element which is released when its temperature is elevated to within a prescribed range, e.g. by the heat from a fire. The outlets of non-automatic sprinklers are maintained normally open, and such sprinklers are operated in an array, as part of a deluge system, from which fire retardant fluid flows when an automatic fluid control valve is activated by a separate fire, e.g. heat, detection system.
Installation or mounting position is another parameter which distinguishes different types of fire protection sprinklers. For example: Pounder U.S. Pat. No. 4,580,729 illustrates a pendent mounting (i.e., pendent-type) sprinkler arranged so that the fluid stream discharged from the outlet is directed initially downwards against the deflector; Dukes U.S. Pat. No. 2,862,565 illustrates an upright mounting (i.e., upright-type) sprinkler arranged so that the fluid stream discharged from the outlet is directed initially upwards against the deflector; and Mears U.S. Pat. No. 4,296,815 and Fischer U.S. Pat. No. 4,296,816 illustrate a horizontal mounting (i.e., horizontal-type) sprinkler arranged so that the fluid stream discharged from the outlet is directed initially horizontally against the deflector. In each case, the purpose of the deflector is to break up the fluid stream into a pattern of spray that can suitably cover the area to be protected by the sprinkler from fire.
ESFR (Early Suppression Fast Response) fire protection sprinkler applications have typically required the use of pendent sprinklers. Upright and horizontal sprinklers have generally been found less suitable for ESFR applications, particularly at commodity storage heights of greater than 30 feet. This is because upright sprinklers inherently have reduced downward spray directly beneath the sprinklers and, therefore, underneath the fire protection fluid supply piping from which they are fed. Horizontal type sprinklers, on the other hand, are generally designed with a spray pattern that projects horizontally to protect more remote reaches of the intended coverage area and, as such, do not provide the downward thrust of fluid spray necessary for ESFR sprinkler applications, over the entire area to be protected from fire by the sprinkler.
The concept underlying ESFR sprinkler technology is that of delivering onto a fire at an early stage a quantity of water sufficient to suppress the fire before a severe challenge can develop. ESFR sprinklers are particularly useful in commercial settings where the clearance between the sprinklers and the source of the fire could be large. For example, in a warehouse having high ceilings, the distance between pendent sprinklers and the upper surfaces of combustible commodities in the storage racks can be relatively large. In such settings, the size of a fire can grow significantly before a first sprinkler is activated by heat from the fire. Thus, it was recognized that to suppress a fire in such a setting, a greater quantity of water should be delivered quickly so that the fire will be kept less intense, and the corresponding convective heat release rate will be kept lower In turn, with a lower heat release rate, the upward plume velocity of the fire will also be relatively lower Fire protection specialists often characterize this concept by saying that the Actual Delivered Density (ADD) of the first operating sprinkler(s) should exceed the Required Delivered Density (RDD). RDD is defined as the actual density of fire retardant fluid required to suppress a fire in a particular combustible commodity in units of gpm/ft2. ADD is generally defined as the density at which water is actually deposited from operating sprinklers onto the top horizontal surface of a burning combustible array, in units of gpm/ft2.
The relationships between sprinkler spray patterns, fire plume velocity, and amount of combustible commodity are important factors which need to be taken into account in the design of ESFR sprinklers. As the ceiling-to-floor distance increases and the amount of combustible commodity increases, the fire plume velocity and upward thrust increase to such vigorous levels that standardized tests now require actual opposing thrust specifications in the central area of the spray pattern for certification of an automatic fire protection sprinkler for service in the ESFR sprinkler category (Ref. Underwriters Laboratories (UL) and Factory Mutual (FM) ESFR Sprinkler Standards). Previous approaches for addressing higher elevation, higher challenge fire protection applications with ESFR pendent sprinklers have included using deflectors with straight slots or slots that taper to become slightly wider in the radially outward direction, in combination with increasing fluid water pressure to compensate for increased elevations, since the thrust of the spray pattern is a combination of both velocity and mass of the fire retardant fluid droplets.
ESFR pendent sprinklers often provide a sprinkler spray pattern having a central downward thrusting core formation. Providing a central core of high thrust droplets is particularly important in higher elevation, higher challenge fire protection applications where the updraft of a quickly developing fire located under a sprinkler head could fully displace the spray pattern of the sprinkler head if the downward thrust was insufficient to effectively oppose the updraft. One approach for providing more water coaxial with the centerline of the sprinkler spray pattern is described in Mears U.S. Pat. No. 4,296,815, the entire disclosure of which is incorporated herein by reference. Mears '815 describes a horizontal sidewall sprinkler with a discharge which increases the amount of fire protection fluid in the region coaxial with the sprinkler discharge axis by use of a deflector with radially extending tines spaced by reentrant slots. A reentrant slot is defined as a cutout extending through a deflector and generally radially inwardly from an opening at the deflector periphery, the slot having a transverse width which is larger at a more radially inward portion of the deflector than the transverse width nearer the peripheral region of the deflector.